EXCEED THE SPACE PROVIDED. The long-term objective of the study is to reduce or delay disability and loss of independence in older adults with walking difficulty. Progressive walking disability is common among older adults, and the deficits characteristic of progressive walking disability contribute to gait inefficiency. Inefficient gait isassociated with fatigue, greater difficulty in activities of daily living (ADL), and risk for future physical disability. In the proposed randomized clinical trial, the specific aim is to determine if for older persons with progressive walking disability, an intervention specifically designed to increase motor skill in walking will improvegait efficiency, increase gait speed, reduce risk for physical disability, and improve physical function and physical activity. A newly developed skill-based gait training intervention addresses the problems characteristic of progressive walking disability of older adults. The randomized clinical trial of skill-based gait training compared to traditional gait training for older persons with progressive walking disability involves gait training intervention 2 times a week for 12 weeks with performance-based and self-report outcomes measured pre (baseline) and post intervention. The study will be conducted at 4 sites, over one year at each site. Participants will be randomized to skill-based or traditional gait training within site. Skill-based gait training is expected to be more effective than traditional gait training in improving gait efficiency and increasing gait speed, associated with reducing mobility-related disability in older persons with progressive walking disability. Clinical and laboratory measure of gait characteristics will be used to address thesecondary objective, to explain changes in gait efficiency and gait speed of older adults after intervention. Additional performance-based and self-report measures of function, endurance, and physical activity will be used to address the secondary objective to determine if improving gait efficiency is associated with improved physical function and reduced risk for physical disability.